I believe this picture has a very, very strong composition. BW is a very good idea in this case. What I like in this shot are the contrast and the fact, that the girls is blurred (depth of field), but honestly there is one thing I don't understand: there is no subject in the sharp plain. I could imagin a boy's face or boy leaning against the wall in the front and this well-shaped girl in the background. This could be a story about a broken love or something.
Anyway, this is a good picture!
Sz.